Assignment 1

 

Assignment No. 1 Mechanical Engineering Department: Jorhat Engineering College Semester : Seventh Date of submission : 16/08/2013

1. A 4 cm diameter water jet with a velocity of 35 m/s impinges on a single vane moving in the same direction at a velocity of 20 m/s. The jet enters the vane tangentially along the x direction. The vane deflects the jet by 150°. Calculate the force exerted by the water w ater on the vane. 2. A water jet 20 mm in diameter and having a velocity of 90 m/s strikes series of moving blades in a wheel. The direction of the jet makes 20° with the direction of movement of the blade. The blade angle at inlet is 35°. If the jet should enter the blade without striking, what should be the blade velocity? If the outlet angle of the blade is 30°, determine the force on the blade. Assume that there is no friction involved in the flow over the blade. 3. Blades are fixed in a disc with outer and inner diameters of 0.8 m and 0.4 m. The disc rotates at 390 rpm. The flow rate through blades is 4000 kg/s. The inlet angle of the blade is 80°. The blade width is 0.25 m. If the flow at outlet is radial, determine the blade outlet angle. Determine the angle at which the water should flow for smooth entry. Determine the torque exerted and the power resulting there from. 4. A jet of water at a velocity of 100 m/s strikes a series of moving vanes fixed at the periphery of a wheel, 5 at the rate of kg/s. The jet is inclined at 20° to the direction of motion of the vane. The blade speed is 50 m/s. The water leaves the blades at an angle of 130° to the direction of motion. Calculate the blade angles at the forces on the wheel whee l in the axial and tangential direction 5. Water jet at the rate of 10 kg/s strikes the series of moving blades at a velocity of 50 m/s. The blade angles with respect to the direction of motion are 35° and 140°. If the peripheral speed is 25 m/s, determine the inclination of the jet so that water enters the blades without shock. Also calculate the power developed and the efficiency of the system. Assume blades and mounting on the periphery of the wheel. 6. Curved vanes fixed on a wheel on the surface receive water at angle of 20° to the tangent of the wheel. The inner and outer diameters of the wheel are 0.9 and 1.6 m respectively. The speed of rotation of the wheel is 7 revolutions per second. The velocity of water at entry is 75 m/s. The water

 

leaves the blades with an absolute velocity of 21 m/s at an angle of 120° with the wheel tangent at outlet. The flow rate is 400 kg/s. Determine the blade angles for shock less entry and exit. Determine the torque and power. A also determine the radial force. 7. A jet of water with a velocity ve locity of 30 m/s impinges on a series of vanes moving at 12 m/s at 30 to the direction of motion. The vane angle at outlet is 162° to the direction of motion. Complete (i) the vane angle at inlet for shock less entry and (ii) the efficiency of power transmission. 8. A jet of 5 cm diameter enters a blade in the x direction with a velocity of 60 m/s. The blade angle at inlet is 0°. The outlet angle is 120° with x direction. If the blade moves with a velocity of 25 m/s along the x direction, determine the forces in the x and y directions. Also determine the energy transfer rate. 9. A jet of water 6 cm diameter has a velocity of 30 m/s. If it impinges on a curved vane which turns the jet by 90° determine forces on the vane if the vane moves in the direction of the jet at a velocity of 14 m/s. 10. A series of vanes is acted upon by a 7.5 cm water jet having a velocity of 30 m/s. α1 = β1 = 0°. If the force acting on the vane in the direction of the jet is 900 N determine the angle by which the jet is turned by the vane. The vane velocity is 15 m/s. 11. A water jet with a velocity of 60 m/s enters a series of curved vanes at an angle of 20° to the direction of blade movement. The peripheral speed of the disc on which the blades are mounted is 25 m/s. Calculate the vane inlet angle. If at the exit the component of absolute velocity along the direction of motion is zero, determine the outlet blade angle. Assume shock less enters and exit.